The inner loop airlift reactor is a new type of reactor developed on the basis of a bubble column. It has a simple structure, no power device therein, and good mass transfer and heat transfer performance, and can be used for gas-liquid, gas-solid and gas-liquid-solid reactions. Therefore, it is widely used in various fields such as fermentation, energy, and sewage treatment.
In the gas-liquid-solid three-phase reaction in which the catalyst is solid particles, the catalyst needs to be recycled in the reactor, and thus the operation of solid-liquid separating is indispensable. There are many methods for separating the solid catalysts, such as sedimentation, filtration, membrane separation, etc., in which the sedimentation method is widely employed. The settlement can be divided into two methods: gravity sedimentation and centrifugal sedimentation. The efficiency of centrifugal sedimentation is far greater than that of gravity sedimentation. A hydrocyclone is a typical separation device using centrifugal sedimentation principle. It has a simple structure, low cost, small land occupancy area, and good separation performance, and is applied widely.
The invention patent of the application publication No. CN105642201A with the application publication date of Jun. 8, 2016 discloses a gas-liquid-solid three-phase loop reactor with flow guide cones. The upper part of a riser of the reactor is installed with a flow guide cone, and the lower part of a downcomer is also installed with a flow guide cone. The restriction of the flow guide cone is beneficial for the gas-liquid-solid mixture to form a circulating flow between the riser and the downcomer, thereby improving the mixing effect of the fluids. The invention patent of the publication No. CN105983377A with the application publication date of Oct. 5, 2016 discloses an internal loop airlift slurry reactor. Although the apparatus is a combination of an internal loop airlift reactor and a hydrocyclone, it has a gas-liquid separation section, a draft tube, and a gas distributor successively disposed inside a housing from top to bottom. A baffled communication section is specifically designed on the upper part of the draft tube, thereby improving the efficiency of gas-liquid separation. A hydrocyclone is disposed on the upper part of the apparatus, for re-separation of gas and liquid, which can effectively solve the problem of entrainment.
In the gas-liquid-solid three-phase reaction, especially for the three-phase reaction in which the catalyst is solid particles, separation of the solid particles from the liquid phase is very important. In the patent CN105642201A, the mixing in the three-phase reaction system is good, but solid-liquid separation cannot be carried out simultaneously in the reactor and correspondingly process intensification of mixing and separating cannot be realized. For the reaction that requires solid separation and recycling, such as Fischer-Tropsch synthesis, an external separation device is highly desired. This method requires additional power and also leads to a more complicated process, which is time-consuming and laborious and increases the land area and operating costs. In an apparatus of patent CN105983377A, although a hydrocyclone with separation effect is added therein, the hydrocyclone is located in a gas-liquid separation zone at the upper part of the reactor and only has the effect of gas-liquid separation. In addition, due to the presence of gas phase, the separation performance of the hydrocyclone is evidently reduced, and the application to the gas-liquid-solid three-phase reaction is limited, especially for situations where fine catalyst particles are present.